EP4242105A1

EP4242105A1 - Buffer for storing liquid at a consumer pressure

Info

Publication number: EP4242105A1
Application number: EP22161620.4A
Authority: EP
Inventors: Hannes MÜLLER
Original assignee: Airbus Operations GmbH
Current assignee: Airbus Operations GmbH
Priority date: 2022-03-11
Filing date: 2022-03-11
Publication date: 2023-09-13
Also published as: US20230287665A1; US12203249B2; CN116733065A

Abstract

The present invention is directed to a buffer (1) for storing liquid at a consumer pressure. The buffer comprises a storage volume (4) for holding a liquid and a gas. The storage volume may be separated by a partition element (5) into a liquid compartment (6) for holding the liquid and a gas compartment (7) for holding the gas. A pressurization means (8) is configured for increasing the pressure of gas in the storage volume (4) to an operating pressure when liquid is or has been drained from the storage volume (4). A ventilation means (14) reduces the pressure of gas in the storage volume (4) back to the operating pressure when the storage volume (4) is filled with liquid. Further, a water supply system (23) for an aircraft (30) comprising the buffer (1) and an aircraft (30) comprising such a water supply system (23) are described and claimed.

Description

The present invention is directed to a buffer for storing liquid at a consumer pressure exceeding environmental pressure. The invention is further directed to a water supply system for an aircraft comprising a buffer and an aircraft comprising a water supply system with a buffer.
EP 3 385 163 A1 discloses an aircraft with a high-pressure water supply and distribution system. The supply and distribution system comprises a water storage tank, at least one pressurization means and at least one piece of consumer equipment. A conduit system supplies water from the water storage tank via the pressurization means to the consumer equipment. The conduit system employs between the pressurization means and the consumer equipment flexible conduits having a maximum internal diameter of 8 mm or less. As compared to existing rigid plumbing, the flexible conduits are significantly easier to install since they do not need to be installed with a constant slope for drainage, require less space and planning and are also less prone to damage caused by water freezing the conduits. Further, the weight of the flexible conduits is also lower.
However, in order to transport water from the central water storage tank to the consumers through the narrow flexible conduits, higher pressures than in conventional water supply systems are typically required. Further, limited flow rates may make it necessary to provide water buffers at the consumer equipment which supply water to the consumer equipment at higher flow rates than provided to the buffers itself.
It is an object of the present invention to provide a buffer for supplying water to one or more consumer equipment on an aircraft. A further object is to provide a water supply system for an aircraft comprising a buffer and an aircraft comprising a water supply system with a buffer.
The object underlying the present invention is solved by a buffer according to claim 1, a water supply system according to claim 10 and an aircraft according to claim 11. Preferred embodiments of the invention are described in the dependent claims.
In a first aspect the invention is direct to a buffer for storing liquid at a consumer pressure exceeding an environmental pressure. The buffer comprises a storage volume for holding the liquid and a gas, a pressurization means for increasing the pressure of gas in the gas compartment and a ventilation means for reducing the pressure of gas in the gas compartment. The pressurization means is configured for increasing the pressure of the gas in the storage volume to an operating pressure or maintaining the pressure of the gas in the storage volume at the operating pressure when liquid is or has been drained from the storage volume. The ventilation means is configured for reducing the pressure of the gas in the storage volume back to the operating pressure or maintaining the pressure of the gas in the storage volume at the operating pressure when the liquid compartment is filled with liquid.
In other words, the buffer comprises a storage volume for holding both the liquid which shall be provided at the consumer pressure as well as a gas. The interface between gas and liquid in the storage volume can be a free surface or a partition element separating both fluids. A buffer with a partition element is described in more detail in a preferred embodiment. In case no partition element is provided, the interface between the liquid and the gas is a free surface formed by gravity. In this case, the pressure of the gas at the interface of the gas and the liquid is equal and, therefore, the operating pressure and the consumer pressure are also equal.
When the pressure of the gas in the storage volume is increased, the pressure of the liquid also increases. Correspondingly, when the pressure of the liquid is reduced, the pressure of the gas in the storage volume is also reduced. This also implies that when the amount or volume of liquid in the storage volume is reduced by draining liquid out of the storage volume, the volume of the gas in the storage volume increases and the pressure of the gas drops. Hence, the pressure of the liquid in the storage volume also drops. On the other hand, when the storage volume is filled up with liquid, i.e., the amount of water in the storage volume is increase, the volume of the gas in the storage volume is reduced and the pressure of the gas in the storage volume rises which causes the pressure of the liquid in the storage volume to rise.
The buffer is configured to provide liquid, in particular, water, at a consumer pressure which is higher than the environmental pressure, for example, to a consumer equipment such as a rinsing of a toilet in an aircraft lavatory or a faucet. The environmental pressure is the pressure of the air surrounding the buffer. For example, in a vented aircraft on the ground the environmental pressure may be the atmospheric pressure. However, when the aircraft is in flight and the cabin of the aircraft is pressurized, the environmental pressure is the cabin pressure. The consumer pressure may, for example, be 2.8 bar.
The liquid is stored at the consumer pressure in the liquid compartment of the buffer. Since the pressure in the storage volume, i.e., the liquid pressure of the buffer, and the pressure of the gas in the storage volume, i.e., the buffer's gas pressure, are correlated, gas in the storage volume is at an operating pressure when liquid in the storage volume is at the consumer pressure. The operating pressure may, for example, be 2.8 bar.
In order to supply water with a constant pressure, the buffer comprises a pressurization means and a ventilation means. The pressurization means is provided for increasing the pressure of gas in the storage volume by pumping additional gas into the storage volume. The pressurization means is configured to increase the pressure in the storage volume, for example, when it drops below the operating pressure or a filling pressure. For example, when liquid is removed from the storage volume of the buffer and the pressure of the gas consequently drops, the pressurization means is activated and increases the gas pressure until it reaches the operating pressure.
On the other hand, when the storage volume of the buffer is filled up with liquid, for example, with water from a high-pressure stage of a high-pressure water supply system, the gas in the storage volume is compressed so that the gas pressure increases and exceeds the operating pressure. In consequence, also the liquid pressure rises above the consumer pressure. To reduce the gas pressure back to operating pressure, the ventilation means is provided for venting gas from the storage volume so that the gas pressure in the buffer drops back to the operating pressure which causes the pressure of the liquid to drop also back to the consumer pressure.
The buffer is particularly advantageous for several reasons. First of all, it enables providing liquid such as water to a consumer equipment at a predetermined consumer pressure. Hence, the buffer can be placed above, below or vertically adjacent to a consumer equipment as it does not rely on gravity to provide water to the consumer equipment.
Further, as compared to buffers which use a pump for pumping liquid out of the buffer to the consumer equipment, the present design is more power and weight efficient. For example, a state of the art toilet rinsing in an aircraft lavatory is a typical application with pulsed flow with a flow rate of approximately 9 l/min for about 1.2 s. The theoretical minimum time between two toilet flushes is about 8 s. A water pump in a buffer needs to able to supply the flow rate of 9 l/min, i.e., roughly 0.18 l of water have to be supplied in 1.2 s. In contrast, in a buffer according to the present invention, the water for a toilet flush is provided largely by the residual gas pressure in the storage volume of the buffer. Hence, the pressurization means can operate at a considerably lower flow rate. Depending on the implementation, it may, for example, be sufficient to have the gas pressure back at the operating pressure before the toilet rinsing can be operated a second time, i.e., in the above example after about 8 s. However, a pressurization means with reduced flow requirements means that the weight and power consumption can advantageously be reduced.
In a preferred embodiment, the storage volume is tightly separated by partition element into a liquid compartment for holding the liquid and a gas compartment for holding the gas. The two compartments thus define the respective parts of the storage volume inside a housing of the buffer which hold the liquid and the gas.
The use of a partition element is preferred since it clearly separates the gas from the liquid. Thus, no gas from the gas compartment can enter a distribution system for the liquid and no liquid may enter the pressurization means supplying the gas or ventilation means. The partition element separates the gas compartment tightly from the liquid compartment, i.e., no liquid can flow through the partition element from the liquid compartment into the gas compartment and no gas can flow from the gas compartment through the partition element into the liquid compartment. Further, the membrane is flexible or movable so that the volume of one of the compartments can be increased by reducing the volume of the other compartment. The partition element can be formed, for example, by a bladder or balloon where the inside of the bladder forms one of the compartments and the other compartment is, for example, defined by the housing of the buffer and an outer surface of the bladder.
In case a partition element is used, it is preferably flexible to have about the same pressure across its interface with the gas and the liquid in the storage volume. Hence, when the pressure in the gas compartment is increased, the pressure in the liquid compartment also increases. Correspondingly, when the pressure in the liquid compartment is reduced, the pressure in the gas compartment is also reduced. Further, this also implies that when the amount or volume of liquid in the liquid compartment is reduced by draining liquid out of the liquid compartment, the pressure of gas in the gas compartment drops and so does the pressure of the liquid in the liquid compartment. On the other hand, when the liquid compartment is filled with liquid, the volume of the gas in the gas compartment is reduced and the pressure of the gas in the gas compartment rises which causes the pressure in the liquid compartment to rise.
In a preferred embodiment the buffer comprises a control means for operating the pressurization means and a pressure sensor arranged in the gas compartment and communicatively connected to the control means. The control means is configured for operating the pressurization means to increase the pressure in the gas compartment to the operating pressure when a pressure measured by the pressure sensor is below the operating pressure.
Hence, in the preferred embodiment a control means, for example, an integrated circuit such as a microcontroller, a microprocessor or an application specific integrated circuit (ASIC), is provided which controls operation of the pressurization means based on a signal received from a pressure sensor. The latter measures the gas pressure in the gas compartment of the buffer. When the pressure in the gas compartment drops below the operating pressure of, for example, 2.8 bar, or filling pressure of, for example, 2.5 bar, the control means activates the pressurization means which fills the gas compartment of the buffer with gas. The control means preferably also halts the filling of gas compartment by the pressurization means when the pressure sensor reports that the gas pressure has reached the operating pressure.
In a preferred embodiment, the pressurization means is a pump, in particular, a diaphragm pump. Diaphragm pumps are particularly preferred as they prevent backflow of gas from the gas compartment. An exemplary diaphragm pump may provide a gas flow of approximately 1.7 l/min at 2.8 bar using less than 30 W power. Corresponding diaphragm pumps are commercially available and weigh less than 250 g.
In a preferred embodiment the ventilation means is a pressure relieve valve adjusted to prevent the pressure in the gas compartment from exceeding the operating pressure. For example, the pressure relieve valve may be adjusted to open when the gas pressure exceeds 2.8 bar.
In an alternative preferred embodiment, the pressurization means and the ventilation means are formed by the same device, i.e., it is conceivable to use the same pump to fill the gas compartment and to also remove gas from the gas compartment.
In a preferred embodiment the buffer is configured such that a rate at which liquid can be drained from the liquid compartment of the buffer exceeds a maximum gas supply rate at which gas can be supplied to the gas compartment of the buffer using the pressurization means such that when liquid is drained from the liquid compartment at a rate exceeding the maximum gas supply rate, the pressure of gas in the gas compartment drops below the operating pressure and can only be increased back to the operating pressure using the pressurization means when no more liquid is drained from the liquid compartment. A buffer according to the preferred embodiment is particularly advantageous as the pressurization means supplying gas to the gas compartment of the buffer does not need to provide an equivalent flow rate to a water pump which would achieve the same liquid flow rates. Thereby, the weight and power consumption of the device can be reduced.
In a second aspect, a water supply system for an aircraft is provided. The water supply system comprises a central water tank, a plurality of pieces of consumer equipment, a conduit system connecting the central water tank to the plurality of pieces of consumer equipment and at least one buffer according to any of the preceding embodiments, where the liquid is water and the gas is air. At least one consumer equipment of the plurality of pieces of consumer equipment is associated with a buffer of the at least one buffer. The at least one buffer is configured to provide water to each associated consumer equipment at the consumer pressure. The water supply system further comprises a central pressurization means for feeding water from the central water tank to the liquid compartment of the at least one buffer at a pressure exceeding the consumer pressure.
The advantages of the water supply system correspond to the advantages of the embodiment of the buffer used therein.
In a further aspect, an aircraft comprising a water supply system according to the any of the preceding embodiments is provided. The advantages of the aircraft correspond to the advantages of the embodiment of the buffer used therein.
Subsequently, the present invention will be described in further detail with regards to the
Figures, wherein

Figure 1: shows a schematical drawing of an exemplary embodiment of a buffer,
Figure 2: shows a schematical drawing of an exemplary embodiment of a water supply system comprising an exemplary embodiment of a buffer and
Figure 3: shows a schematical drawing of an exemplary embodiment of an aircraft with an exemplary embodiment of a water supply system comprising an exemplary embodiment of a buffer.

Throughout the Figures like elements are designated with like reference numerals.
Figure 1 shows an exemplary embodiment of a buffer 1 for providing a liquid in the form of water at a consumer pressure to a consumer equipment. The consumer equipment itself is not shown in Figure 1. However, a consumer supply line 2 connecting the buffer 1 to the consumer equipment is shown. The buffer 1 comprises a housing 3 defining a storage volume 4 for holding a liquid and a gas. In the exemplary embodiment, the storage volume 4 is separated by a partition element 5 into a liquid compartment 6 which holds the water in the storage volume 4 and a gas compartment 7 for holding the air in the storage volume 4.
The partition element 5 seals the liquid compartment 6 from the gas compartment 7 thereby forming a barrier preventing water from entering the gas compartment 7. Likewise, gas is prevented from flowing from the gas compartment 7 to the liquid compartment 6. The partition element is further configured so that the volume of the liquid compartment 6 can be increased by reducing the volume of the gas compartment 7 and vice versa. Further, the pressure of the air in the gas compartment 7 and the pressure of the water in the liquid compartment 6 are positively correlated. Hence, when the pressure of the air in the gas compartment 7 rises, the pressure of the water in the liquid compartment 6 also rises. Since the pressure of the water in the liquid compartment 6 is positively correlated with the pressure of the air in the gas compartment 7, the air is held at an operating pressure in the gas compartment 7 when the water is held at the consumer pressure in the liquid compartment 6. The partition element 5 is formed from a flexible membrane so that the pressure of the gas along the membrane and the pressure of the water along the membrane are about equal.
Water shall be supplied from the buffer 1 at a consumer pressure which exceeds the environmental pressure. In case the buffer 1 is used onboard an aircraft, the environmental pressure corresponds to the cabin pressure. When the aircraft is on the ground and the cabin is vented, the cabin pressure corresponds to the atmospheric pressure. However, when the aircraft is in flight and the cabin is pressurized, the cabin pressure and, thus, the environmental pressure may be above the atmospheric pressure.
The buffer 1 further comprises a pressurization means 8 in form of a diaphragm pump 9. The pressurization means 8 is connected to the gas compartment 7 of the storage volume 4 via a gas opening 10 and can be operated to supply air to the gas compartment 7. In the exemplary embodiment shown in Figure 1, the diaphragm pump 9 can supply air at a flow rate of 1.7 l/min at a pressure of 2.8 bar to the storage volume 4. The power consumption of the diaphragm pump 9 is less than 30 W and it weighs less than 250 g. Using a diaphragm pump 9 as a pressurization means 8 has the advantage that it intrinsically prevents backflow of air from the gas compartment 7. The pressurization means 8 is used to supply air to the gas compartment 7 when water has been drained from the liquid compartment 6 to bring the pressure in the gas compartment 7 back to the operating pressure.
To this end, a gas pressure sensor 11 is part of the buffer 1 which measures the pressure of the air in the gas compartment 7 of the storage volume 4. The pressure sensor 11 is communicatively connected to a control means 12 which controls amongst others the operation of the pressurization means 8 via a control line 13. In the exemplary embodiment shown in Figure 1, the control means 12 is a microcontroller which is configured to read the values form the pressure sensor 11 and control the operation of the diaphragm pump 9. The control means 12 turns the diaphragm pump 9 on when the pressure in the gas compartment 7 as sensed by the pressure sensor 11 reaches a filling threshold which may, for example, be 0.3 bar below the operating pressure, i.e., when the operating pressure is at 2.8 bar, the filling threshold would be 2.5 bar. Hence, the diaphragm pump 9 is turned on by the control means 12 when the pressure measured by the pressure sensor 11 drops below 2.5 bar.
The control means 12 also turns the diaphragm pump 9 off when the pressure measured by the pressure sensor 11 in the gas compartment 7 of the buffer 1 reaches the operating pressure. Thus, in the embodiment shown in Figure 1, the diaphragm pump 9 is turned off, when the pressure in the gas compartment 7 reaches 2.8 bar.
In order to release air from the gas compartment 7 of the buffer 1, a ventilation means 14 in form of a relief valve 15 is provided. The relief valve 15 is also connected to the gas opening 10 of the storage volume 4 so that the buffer 1 in the example shown in Figure 1 comprises only one opening for filling the gas compartment 7 with gas and removing gas therefrom. The relief valve 15 is configured to automatically open when the pressure in the gas compartment 7 exceeds the operating pressure of, for example, 2.8 bar. In the embodiment in Figure 1 the relieve valve 15 is a passive device which opens automatically when the pressure in the gas compartment 7 exceeds the operating pressure and closes automatically when the pressure in the gas compartment 7 is at or below the operating pressure.
The buffer 1 further comprises a liquid opening 16 which is provided for supplying water to the liquid compartment 6 of the storage volume 4 and for removing water from the liquid compartment 6. Water is supplied to the liquid compartment 6 and, thus, to the storage volume from a central water tank which is not shown in Figure 1. However, a line 17 connecting the buffer 1 to the central water tank is shown in Figure 1. The line 17 is connected to the liquid opening 16 of the buffer 1 and comprises a fill valve 18 for controlling the supply of water from the central water tank.
Opening and closing of the fill valve 18 is also controlled by the control means 12. The control means 12 opens the fill valve 18, when water has been removed from the storage volume 4 for supplying water to a consumer equipment and closes the fill valve 18 when the liquid compartment 6 has been filled with water, for example, up to a maximum fill level. In the exemplary embodiment shown in Figure 1, two fill level sensors 20, 21 are provided. Both fill level sensors 20, 21 are communicatively connected to the control means 12. The latter is configured, for example, to close the fill valve 18 when the water level in the liquid compartment reaches the upper fill level sensor 21. The fill valve 18 may open when level is lower than the lower fill level sensor 20. A redundancy check included in the control means 12 verifies, for example, whether the lower level sensor 20 was also activated while the higher level sensor 21 gets active.
Finally, a protective release valve 22 is provided in the consumer supply line 2. The protective release valve 22 is configured such that it opens when a maximum operating pressure is exceeded. Thereby, the equipment is protected from damage caused by high water pressure which is in particularly useful if a high-pressure water supply system is used to supply water from the central water tank to the buffer 1.
The buffer 1 shown in Figure 1 is operated as follows: when water is requested from a consumer equipment connected to the consumer supply line 2, for example, by opening a valve at the consumer equipment, water is pushed out of the storage volume 4 due to the pressurized gas in the gas compartment 7 of the storage volume 4 and thus supplied to the consumer equipment. When the water level in the storage volume 4 drops, the volume of the gas compartment 7 and, thus, the storage volume increases and the gas pressure drops. Once the pressure sensed by the pressure sensor 11 drops below the filling threshold, the control means 12 activates the pressurization means 8 which supplies air to the gas compartment to increase the gas pressure. When the pressure in the gas compartment reaches the operating pressure, the pressurization means 8 is shut off by the control means 12.
In case the consumer equipment is, for example, a toilet in an aircraft lavatory, the water flow to be provided by the buffer 1 is pulsed. For example, a state of the art toilet rising takes up water at a flow rate of approximately 9 l/min for about 1.2 s. Subsequent toilet flushes are separated by at least 8 s. Thus, the flow that needs to be provided by the buffer 1 is highly pulsed. Since the residual gas pressure in the gas compartment 7 of the buffer 1 is preferably sufficient to provide water for several toilet flushes, the pressurization means 8 does not have to supply the gas with the same flow at which water is removed from the buffer 1. Hence, as compared to a pump provided in a buffer which provides water from the buffer 1, the pressurization means 8 takes up less power and weighs less.
Figure 2 shows a schematic drawing of an exemplary embodiment of a water supply system 23 for an aircraft. The water supply system 23 comprises a central water tank 24 which is connected via low-pressure plumbing 25 to a high-pressure water pump 26 which provides water from the central water tank 24 to various pieces of consumer equipment 27a to 27d via a high-pressure conduit system 28. The pieces of consumer equipment 27a to 27d are collectively referred to as consumer equipment 27. Each consumer equipment 27a to 27d is associated with a buffer 1a to 1c as shown in Figure 1. The buffers 1a to 1c are collectively identified using the reference numeral 1. The consumer equipment 27a is a toilet rinsing which is arranged in the same lavatory (not shown) as a sink forming the consumer equipment 27b. The two pieces of consumer equipment 27a, 27b arranged in the same lavatory are supplied by the same buffer 1a. The other two pieces of consumer equipment 27c, 27d, a sink in a galley and steam oven, are supplied from individual buffers 1b and 1c. With regard to the details of the buffers 1a to 1c reference is made to Figure 1 and the corresponding description.
The high-pressure water supply conduit system 28 is made-up from flexible conduits 29 made from a plastic material with an internal diameter of, for example, 4 - 6 mm. The buffers 1a to 1c store the water at a consumer pressure of, for example, 2.8 bar at which the water can be directly supplied to the consumer equipment 27a to 27d.
Finally, Figure 3 shows an exemplary embodiment of an aircraft 30 with an exemplary embodiment of a water supply system 23 as shown in Figure 2. With regard to the details of the water supply system 23, reference is made to Figure 2 and the corresponding parts of the description.

Claims

A buffer (1) for storing liquid at a consumer pressure exceeding an environmental pressure comprising
a storage volume (4) for holding the liquid and a gas,

a pressurization means (8) configured for increasing a pressure of the gas in the storage volume (4) to an operating pressure or maintaining the pressure of the gas in the storage volume at the operating pressure when liquid is or has been drained from the storage volume (4) so that the pressure of liquid in the storage volume (4) is increased to the consumer pressure, and

a ventilation means (14) configured for reducing the pressure of the gas in the storage volume (4) back to the operating pressure or maintaining the pressure of the gas in the storage volume at the operating pressure when the storage volume (4) is filled with liquid so that the pressure of the liquid in the storage volume (4) is reduced to the consumer pressure.
Buffer (1) according to claim 1, wherein the storage volume is tightly separated by a partition element (5) into a liquid compartment (6) for holding the liquid and a gas compartment (7) for holding the gas, wherein the partition element (5) is configured such that a volume of the liquid compartment (6) can be increased by reducing a volume of the gas compartment (7) and vice versa.
Buffer (1) according to claim 2, wherein the partition element (5) is a membrane or diaphragm.
Buffer (1) according to any of the preceding claims, wherein the buffer (1) comprises a control means (12) for operating the pressurization means (8) and a pressure sensor (11) arranged in the gas compartment (7) and communicatively connected to the control means (12), wherein the control means (12) is configured for operating the pressurization means (8) to increase the pressure in the gas compartment (7) to the operating pressure when a pressure measured by the pressure sensor (11) is below the operating pressure.
Buffer (1) according to any of the preceding claims, wherein the pressurization means (8) is a pump (9), in particular, a diaphragm pump (9).
Buffer (1) according to any of the preceding claims, wherein the ventilation means (14) is a pressure relieve valve (15) adjusted to prevent the pressure in the gas compartment (7) from exceeding the operating pressure.
Buffer (1) according to any of claims 1 to 5, wherein the pressurization means (8) and the ventilation means (14) are formed by the same device.
Buffer (1) according to any of the preceding claims, where the gas is air, and the liquid is water.
Buffer (1) according to any of the preceding claims, wherein the buffer (1) is configured such that a rate at which liquid can be drained from the liquid compartment (6) of the buffer (1) exceeds a maximum gas supply rate at which gas can be supplied to the gas compartment (7) using the pressurization means (8) such that when liquid is drained from the liquid compartment (6) at a rate exceeding the maximum gas supply rate, the pressure of gas in the gas compartment (7) drops below the operating pressure and can only be increased back to the operating pressure using the pressurization means (8) when no more liquid is drained from the liquid compartment (6).
A water supply system (23) for an aircraft (30) comprising
a central water tank (24),

a plurality of pieces of consumer equipment (27),

a conduit system (28) connecting the central water tank (24) to the plurality of pieces of consumer equipment (27),

at least one buffer (1) according to any of the preceding claims, wherein at least one consumer equipment (27) of the plurality of pieces of consumer equipment (27) is associated with a buffer (1) of the at least one buffer (1) and wherein the at least one buffer (1) is configured to provide water to each associated consumer equipment (27) at the consumer pressure, and

a central pressurization means (26) for feeding water from the central water tank (24) to the liquid compartment (6) of the at least one buffer (1) at a pressure exceeding the consumer pressure.
An aircraft (30) comprising a water supply system (23) according to the preceding claim.